Magnetically confined ion getter pump having combined coupling flange and pole piece structure



April 23, 1968 P. w. HAIT 3,379,365

MAGNETIC/ALLY CONFINED ION GETTER PUMP HAVING COMBINED COUPLING FLANGE AND POLE PIECE STRUCTURE Filed Aug. 15, 1966 2 Sheets-Sheet 1 INVENTOR.

PAUL W HAIT L we ATTORNEY 3,379,365 BINED April 23, 1968 w. HAlT MAGNETICALLY CONFINED ION GETTER PUMP HAVING COM COUPLING FLANGE AND POLE- PIECE STRUCTURE Filed Aug. 15, 1966 2 Sheets-Sheet INVENTOR.

United States Patent 3,379,365 MAGNETICALLY CONFINED ION GETTER PUMP HAVING COMBINED COUPLING FLANGE AND POLE PIECE STRUCTURE Paul W. Hait, Los Altos, Califl, assiguor to Varian Associates, Palo Alto, Calif., a corporation of California Filed Aug. 15, 1966, Ser. No. 572,305 7 Claims. (Cl. 23069) The present invention relates in general to magnetically confined glow discharge ion getter vacuum pumps and, more particularly, to an improved vacuum pump which is designed for in-line use by being flanged at both ends and which economizes on both cost and Volume by having its flanges made of magnetic material to also serve as the .pole pieces for the magnetic structure of the pump. Such improved pumps are especially useful, but not limited to, for in-line use Where it is desired to insert a vacuum pump into an existing tubulation. In such as case, the existing tubulation need only he parted, a portion removed, flanges installed and the vacuum pump inserted. The ends of the parted tubulation would ordinarily support the pump of the present invention.

Heretofore, in-line magnetically confined glow discharge getter ion vacuum pumps have been built. However, in these prior pumps the magnetic pole piece structure of the magnetic circuit was separated from the flange structure for coupling the pump to the tubulation to be exhausted. Such a prior art pump is described and claimed in United States Patent 3,125,283 issued Mar. 17, 1964, and assigned to the same assignee as the present invention. The problem with such a prior pump structure is that its overall axial length is substantially increased by the provision of the separate flange assemblies. In many applications, especially where relatively low pumping speeds, i.e., on the order of s of liters/second or less are required, there is not suflicient space to accommodate the axial length of the prior design.

In the present invention, the overall axial length of the pump is subsequentially reduced, especially for relatively low pumping speed pumps, by making the coupling flange portions of the pump of a magnetic material, whereby the flanges perform the additional function of the magnetic pole piece structure for the pump.

The principal object of the present invention is the provision of an improved getter ion vacuum pump.

One feature of the present invention is the provision of magnetic coupling flange assembly, whereby the flange assembly serves as a portion of the magnetic circuit of the vacuum pump to reduce the overall axial length of the pump.

Another feature of the present invention is the same as the preceding feature wherein a pair of magnetic flange assemblies are provided on opposite axial ends of the pump, whereby the pump is especially well adapted for in-line use.

Another feature of the present invention is the same as any one or more of the preceding features wherein the magnetic flange assembly is made of magnetic stainless steel, whereby the flange maintains its strength and cleanliness under normal baking conditions.

Other features and advantages of the present invention will become apparent upon a perusal of the following specification taken in connection with the accompanying drawings wherein:

FIG. 1 is a longitudinal sectional view of a vacuum pump of the present invention as installed in a section of tubulation to be evacuated,

FIG. 2 is a sectional view of the structure of FIG. 1 taken along line 22 of FIG. 1 partially broken away,

FIG. 3 is a sectional view of an alternative embodi- Patented Apr. 23, 1968 ment of a portion of the structure of FIG. 1 delineated by line 3-3, and

FIG. 4 is a sectional view of the structure of FIG. 3 taken along line 4-4 in the direction of the arrows.

Referring now to FIG. 1 there is shown the vacuum pump 1 of the present invention as connected in-line with a section of tubulation 2, as of 1.25" inside diameter, to be evacuated. The pump 1 includes a pair of axially spaced coaxially aligned magnetically permeable annular flange members 3 as of 0.5 thick and 3.25" outside diameter magnetic 430 stainless steel. The flanges 3 are welded at 4 to opposite annular end walls 5 of a cylindrical vacuum envelope section 6 as of 3.75" inside diameter non-magnetic 304 stainless steel. A pair of annular getter cathode plates 7, as of titanium, are disposed adjacent the ends of the cylindrical envelope section 6. A circular array of cylindrical anode cells 8 each of 1.0" in length and 0.715" in diameter surrounds a central anode cell 9 which is, for example, 1.0" in length and 1.5" inside diameter. The cells 8 and 9 are held together by spot welding at their points of contact to form the anode array of glow discharge passageways.

An anode feedthrough insulator assembly 11 is mounted in the side wall of the envelope section 6 and includes an anode support rod 12 which is connected to the anode array as by spot welding to a metallic support band 13 which in turn is spot Welded to the anode cells 8. Three wedge shaped ceramic insulator members 14, as of alumina ceramic, hold the cathode plates 7 apart and are wedged inwardly against the anode array at intervals to prevent transverse movement of the anode.

A pair of C-shaped permanent magnets 15 are co pled between the flanges 3 externally of the vacuum envelope 6 to magnetically polarized one of the flanges 3 as a north pole and the other flange 3 as a south pole. A magnetic field H is, thus, produced between the flanges 3 which threads through the envelope 6, cathode plates 7 and anode cells 8. An axially directed fringing magnetic field H is also produced which threads axially through the central cell 9, as indicated. The magnets 15 are held onto the magnetic flanges 3 via volts 16, threaded into tapped bores 17 in the flanges 3, and which pass through bores in the magnets 15.

A power supply 18 supplies a positive potential relative to ground, as of 3 kv., to the anode via feedthrough insulator assembly 11. The remaining portion of the pump, including the cathode plates 7, is operated at ground potential.

Flanges 3 mate with similar non-magnetic flanges 21 which are brazed to the adjacent sections of tubulation 2. The abutting faces of the flanges 3 and 21 are provided with a matched set of annular grooves at 22 to form a conventional demountable vacuum tight joint when a soft metal gasket 23 is squeezed between the grooved faces of the flanges 3 and 21. Flanges 21 and 3 are pulled together by means of a plurality of cap screws 24 which pass through holes bored in the outer flanges 21 and are threaded into tapped holes in the pump flanges 3.

In operation, the tubu-lation 2 and the pump 1 are evacuated by a roughing pump, not shown, to a suitable pressure as l l0 torr. The power supply 18 is then energized and the operating potentials are applied 'between anode and cathode of the pump 1. A plurality of cold cathode glow discharge columns appear in each of the anode cells 8 and the central cell 9. Positive ions produced in the glow discharge columns within cells 8 bombard the cathode plates 7 to produce sputtering of the titanium getter material which is deposited on various surfaces within the pump, including the anode surfaces, where it serves to getter gas coming in contact therewith. The central cell 9 also produces a glow discharge but the ions, which are focused into a beam 25 along the axis of 3 the cell 9, pass through into the adjacent sections of tubulation 2.

The pump 1 of the present invention is especially useful as it may be accommodated readily in various vacuum systems to augment other vacuum pumps merely by parting the existing tubulation of the system, afiixing flanges 21 to the severed ends of the tabulation, and inserting the pump 1. The pump 1 requires a minimum of space since its flanges 3 also serve as the pole structure of the pumps magnetic circuit. In addition, the pump 1 is supported by the tubulation 2 without the requirement of separate support brackets and the like.

Referring now to FIG. 3 and 4 there is shown an alternative embodiment of the pump 1 of the present invention. In this embodiment a pair of cathode plates 26 are suspended at opposite ends of the central anode cell 9 facing toward the cell 9. The cathode plates 26 are made of getter material such as titanium and are held in position by means of a spider 27, as of. 0.030 thick 304 stainless steel, having four radial leg portions captured at their ends between the flange 3 and the cathode plates 7. The spider 27 is easily formed by punched part techniques and includes four tab members 28 which are bent over the edge of the cathode plate portions 26 to hold the cathode plates 26 in position. The open spaces between the legs of the spider 27 provide axial perforations which permit gas access to the pump 1.

The cathode plates 26 are sputtered by the ion beam 25 to provide additional pumping speed. The low pressure regime pumping speed for the pump 1 is enhanced by the provision of the cathode plates 26 since the larger diameter anode cell 9 sustains its glow discharge to lower pressures than the smaller diameter cells 8.

Since many changes could be made in the above construction and many apparently widely diflerent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illstrative and not in a limiting sense.

What is claimed is:

1. A getter ion magnetically confined glow discharge pump apparatus including; means forming a hollow vacuum envelope; means forming an anode structure disposed within said envelope; means forming a cathode structure disposed within said envelope and including portions to be bombarded by positive ions to cause sputtering of cathode material for gettering gas within said envelope and being spaced from said anode structure on opposite sides of said anode structure with said anode structure disposed therebetween; means forming a magnetic structure disposed on opposite sides of said anode structure for applying a magnetic field which threads through said envelope, said anode, and said spaced cathode portions; means for partitioning said anode structure into a plurality of glow discharge passageways distributed transversely to the direction of the magnetic field threading through said anode and serving to enhance the glow discharges through said passageways; means forming a coupling flange at one end of said envelope for coupling the pump to apparatus to be evacuated, and wherein said coupling flange is of magnetic material forming a portion of said magnetic structure of the pump apparatus, whereby the overall size of the pump is reduced compared to similar pumps having separate flange and magnetic structure portions.

2. The apparatus of claim 1 wherein said envelope includes means forming a second coupling flange structure disposed on the opposite end of said envelope from said first flange, and wherein said second coupling flangeis of magnetic material and forms a portion of said magnetic structure of the pump.

3. The apparatus of claim 2 including a permanent magnet disposed externally of said envelope and coupled between said first and second coupling flanges to magnetically polarize one of said flanges with a north pole polarity and the other flange with a south pole polarity and to produce the magnetic field threading through said anode structure.

4. The apparatus of claim 3, wherein said magnetic coupling flanges include annular grooved face portionsat opposite ends of said envelope and facing away from each other to form a demountable flange assembly for coupling to the flanged apparatus to be evacuated.

5. The apparatus of claim 4 wherein said grooved magnetic flanges are made of magnetic stainless steel, whereby baking of the pump is facilitated.

6. The apparatus of claim 4 wherein said anode is partitioned into an annular array, of glow discharge passageways, said magnetic flanges are annular and coaxially aligned at opposite ends of said envelope, and said annular array of anode glow discharge passageways is coaxially aligned with said annular flanges.

7. The apparatus of claim 6 wherein said anode array includes a central discharge passageway coaxially disposed of said annular flanges and surrounded by an array of anode passageways having lesser transverse dimensions, and wherein said cathode structure includes an axially perforated portion coaxia-lly aligned with said central passageway to provide a cathode portion for sputtering by ions generated within said central passageway while permitting gas access therethrough, whereby the pumping speed of the pump is enhanced at gas pressures below which said anode passageways of lesser transverse dimensions begin to appreciably lose their pumping speed.

References Cited UNITED STATES PATENTS ROBERT M. WALKER, Primary Examiner. 

1. A GETTER ION MAGNETICALLY CONFINED GLOW DISCHARGE PUMP APPARATUS INCLUDING; MEANS FORMING A HOLLOW VACUUM ENVELOPE; MEANS FORMING AN ANODE STRUCTURE DISPOSED WITHIN SAID ENVELOPE; MEANS FORMING A CATHODE STRUCTURE DISPOSED WITHIN SAID ENVELOPE AND INCLUDING PORTIONS TO BE BOMBARDED BY POSITIVE IONS TO CAUSE SPUTTERING OF CATHODE MATERIAL FOR GETTERING GAS WITHIN SAID ENVELOPE AND BEING SPACED FROM SAID ANODE STRUCTURE ON OPPOSITE SIDES OF SAID ANODE STRUCTURE WITH SAID ANODE STRUCTURE DISPOSED THEREBETWEEN; MEANS FORMING A MAGNETIC STRUCTURE DISPOSED ON OPPOSITE SIDES OF SAID ANODE STRUCTURE FOR APPLYING A MAGNETIC FIELD WHICH THREADS THROUGH SAID ENVELOPE, SAID ANODE, AND SAID SPACED CATHODE PORTIONS; MEANS FOR PARTITIONING SAID ANODE STRUCTURE INTO A PLURALITY OF GLOW DISCHARGE PASSAGEWAYS DISTRIBUTED TRANSVERSELY TO THE DIRECTION OF THE MAGNETIC FIELD THREADING THROUGH SAID ANODE AND SERVING TO ENHANCE THE GLOW DISCHARGES THROUGH SAID PASSAGEWAYS; MEANS FORMING A COUPLING FLANGE AT ONE END OF SAID ENVELOPE FOR COUPLING THE PUMP TO APPARATUS TO BE EVACUATED, AND WHEREIN SAID COUPLING FLANGE IS OF MAGNETIC MATERIAL FORMING A PORTION OF SAID MAGNETIC STRUCTURE OF THE PUMP APPARATUS, WHEREBY THE OVERALL SIZE OF THE PUMP IS REDUCED COMPARED TO SIMILAR PUMPS HAVING SEPARATE FLANGE AND MAGNETIC STRUCTURE PORTIONS. 